Certain laser scanning projection devices such as wafer defect scanners, laser printers, document scanners, projectors and the like often employ a collimated laser beam that scans across a flat surface in a straight line path. These devices employ tilting mirrors to deflect the collimated laser beam to perform the scanning. These tilting mirrors may be, or may include, Micro Electro Mechanical Systems (“MEMS”) devices. The actuation of mirrors used in MEMS devices, referred to herein as MEMS mirrors, can be via the electromagnetic, electrostatic, piezoelectric, and thermoelectric effects, depending on application.
One type of common MEMS mirror includes a stator and a rotor, with the rotor or structures carried by the rotor being reflective. The stator and/or rotor are driven with a drive signal which results in the rotor oscillating with respect to the stator, thereby changing the angle of reflectance of an incident light beam on the rotor. By oscillating the rotor between two orientations, an opening angle of the mirror is defined, and scanning of the light beam across the flat surface is accomplished.
MEMS mirrors used in applications that utilize fast scanning rates (typically over 20 Khz) are often resonance mirrors due to the relative ease of maintaining a mirror at resonance as opposed to providing specific drive controls selecting travel limits for the mirrors or setting oscillation frequencies for the mirrors. Therefore, for these applications, it is desired to be able to precisely drive and maintain the mirrors at resonance. This is one area in which development is needed.
Naturally, precise control of the movement of the mirror is but one aspect of laser scanning projection devices. Another aspect is precise control of the collimated laser beam itself so as to ensure that the desired image or video is clearly displayed, with accurate colors. To that end, laser scanning projection devices typically include an application processor, a projection subsystem, and an optical module. The application processor functions to deliver a video stream to the projection subsystem. The projection subsystem processes the video stream and based upon that processing, properly drives the optical module so as to project the video onto a surface for viewing.
Typically, the projection subsystem includes an application specific integrated circuit (ASIC) that receives the video input from the application processor and controls a laser source driver and a mirror controller appropriately so as to effectuate control of the optical module by the laser source driver and mirror controller to project the video. The ASIC must be specifically designed to work with the geometry of the specific optical module used, and with the opening characteristics of the laser source driver, to keep the white point of the projected image constant over time.
Since the ASIC must be specifically designed, the cost of developing a laser projection system is higher than desired, since no “off the shelf” solution exists for the functionality provided by the ASIC. For each application, a new ASIC must be specifically designed. In order to lower the cost of development, further development in this area is also needed, here so as to provide for an “off the shelf” hardware solution.